Normal and Abnormal Patterns of 18F-Fluorodeoxyglucose PET/CT in Lymphoma

Cross-sectional evaluation of thoracic lymphoma

Thoracic lymphomas most frequently involve mediastinal lymph nodes in the anterior mediastinum and paratracheal areas. The lymphomas may also involve lung, thymus, pleura, pericardium, chest wall, and the breast and their radiologic manifestations are diverse. Lymphomas (mostly BALT lymphoma and large B-cell lymphoma) may arise primarily from the lung with various imaging features including single or multiple nodule(s) and area(s) of consolidation. CT is currently the most important imaging modality for the evaluation of thoracic lymphoma but FDG PET also plays a crucial role in the clinical management of these cases.

Cross-sectional evaluation of thoracic lymphoma

In patients who have lymphoma, the presence and distribution of thoracic involvement is important in both tumor staging and treatment. Thoracic involvement in Hodgkin lymphoma (HL) is more common than in non-Hodgkin lymphoma (NHL). In HL, mediastinal lymphadenopathy with contiguous spread is a hallmark, and lung parenchymal involvement at the initial presentation is almost always associated with mediastinal lymphadenopathy. NHL is more heterogeneous and generally presents at a more advanced stage than HL. Most often, mediastinal involvement occurs as a disseminated or recurrent form of extrathoracic lymphoma. Bulky mediastinal disease with compression of adjacent structures can occur, particularly with high-grade subtypes of NHL and isolated lung disease without mediastinal lymphadenopathy can occur in contrast to HL.

Hodgkin's and Non-Hodgkin's Lymphomas

The diagnosis and management of lymphoma have undergone significant changes in the past 20 years. For example, new immunophenotypic and molecular methods have replaced traditional histology-based classification schemes for lymphoma. Fluorine-18-deoxyglucose (FDG) positron emission tomography (PET) has evolved into a potent staging tool and prognostic indicator in many kinds of lymphoma. The role of radiation therapy, especially in patients who have early-stage Hodgkin's disease, has changed substantially. The introduction of anti-CD 20 antibody therapy (Rituximab) has improved the treatment of B-cell lymphoma. These changes are linked with higher expectations for imaging, such as detection of more subtle lymphoma manifestations, evaluation of residual changes, and better assessment of early response. This article reviews clinical and radiologic features of both Hodgkin's disease and non-Hodgkin's lymphoma. It also describes the radiologic staging of lymphoma and the emerging role of FDG-PET for assessing lymphoma.